1. Field of the Invention
The invention relates to the field of photography, and particularly to a photosensitive materials processing apparatus.
1. Description of the Prior Art
The processing of photographic film involves a series of steps such as developing, bleaching, fixing, washing, and drying. These steps lend themselves to mechanization by conveying a continuous web of film or cut sheets of film or photographic paper sequentially through a series of stations or tanks, each one containing a different processing liquid appropriate to the process step at that station.
There are various sizes of photographic film processing apparatus, i.e., large photofinishing apparatus and microlabs. A large photofinishing apparatus utilizes tanks that contain approximately 100 lits of each processing solution. A small photofinishing apparatus or microlab utilizes tanks that may contain less than 10 liters of processing solution.
The chemicals contained in the photographic solution: cost money to purchase; change in activity and leach out or season during the photographic process; and after the chemicals are used the chemicals must be disposed of in an environmentally safe manner. Thus, it is important in all sizes of photofinishing apparatus to reduce the volume of processing solution. The prior art utilized various types of replenishing systems that add or subtract specific chemicals to the photographic solution to maintain a consistency of photographic characteristics in the material developed. It is possible to maintain reasonable consistency of photographic characteristics only for a certain period of replenishment. After a photographic solution has been used a given number of times, the solution is discarded and a new photographic solution is added to the tank.
Activity degradation due to instability of the chemistry, or chemical contamination, after the components of the photographic solution are mixed together causes one to discard the photographic solution in smaller volume tanks more frequently than larger volume tanks. Some of the steps in the photographic process utilize photographic solutions that contain chemicals that are unstable, i.e., they have a short process life. Thus, photographic solutions in tanks that contain unstable chemicals are discarded more frequently than photographic solutions in tanks that contain stable chemicals.
The prior art suggest, that if the volume of the various tanks contained within various sizes of photographic processing apparatus were reduced, the same amount of film or photographic paper may be processed, while reducing the volume of photographic solution that was used and subsequently discarded. One of the problems encountered by the prior art in using smaller volume tanks was that the inner and outer sections of the tank were fixed and not separable.
Another problem encountered by the prior art in using low volume tanks was that fresh processing solution had to be placed in the small space between the processing surfaces of the photosensitive material and the processing solution exiting wall of the processing chamber. If one just attempted to pump fresh processing solution between the wall of the processing chamber and the photosensitive material, the fresh processing solution would not migrate directly to the photosensitive material since the space was small and there was low chemical activity. Hence, the photosensitive material would not be developed properly. Thus, the prior art needed a way to introduce fresh processing solution between a wall and the surfaces of a photosensitive material.
Nozzles or holes were used by the prior art to distribute fresh processing solution in large volume processing tanks. However, if one used nozzles or holes to distribute fresh processing solution in small volume processing tanks, the photosensitive material would not be uniformly developed. The reason for the above is that when the fresh processing solution was distributed, the fresh processing solution was close to the photosensitive material and did not have space to uniformly spread out across the surfaces of the photosensitive material. If the distance between the nozzles or holes and the surface of the photosensitive material were increased to obtain adequate distribution of the fresh processing solution, one would no longer have a small volume tank.
Slots were not used by the prior art to distribute fresh processing solution in large volume tanks since the processing solution would not travel uniformly across a large volume of solution.
As the photosensitive material passes through the tank, a boundary layer is formed between the surfaces of the photosensitive material and the processing solution. The processing solution moves with the photosensitive material. Thus, the boundary layer between the photosensitive material and the processing solution has to be broken up to enable fresh processing solution to reach the photosensitive material. Rollers were used in large prior art tanks to break up the boundary layer. The roller squeegeed the exhausted processing solution away from the surfaces of the photosensitive material, thus, permitting fresh processing solution to reach the surfaces of the photosensitive material. One would not use rollers in small volume tanks, to break the boundary layer between the photosensitive material and the processing solution, since rollers require additional space and add to the volume of required processing solution.
Wire meshes were utilized by the prior art to break the boundary layer to uniformly distribute fresh processing solution across the surfaces of the photosensitive material. One of the difficulties encountered in using wire mesh was that the mesh would catch particulate matter which abrades the photosensitive material surfaces causing pressure sensitization and scratches. The mesh material also wears which causes a nonuniform reaction between the processing solution and the photosensitive material. Furthermore, the mesh must be cleaned or replaced.